1. Field of Invention
This invention relates generally to the field of apparatus and methods for storing, mixing, metering, and pumping polymeric slurry chemical. Moreover it pertains specifically to such apparatus for drag reducing agent slurry injection into a pipeline.
2. Prior Art
Many devices have been proposed for storing, mixing, metering, and pumping polymeric slurries. No known patents exist for these devices. However, these devices are limited in their functionality, due in part to inferior construction, poor design, failed reliability, misused component parts, lack of chemistry knowledge concerning the slurry properties, piping code violations, electrical code violations, and OHSA violations. This invention embodies improved methods and apparatus that overcome these deficiencies in a unique and new means.
Most previously offered devices in the area of polymeric slurry storage and pumping have been devised by trial and error with no engineering design or project structure. The chemical has been stored in horizontal containers or square containers with limited or no recirculation methods. This allowed the solids component of the chemical polymeric slurry to settle in the dead zones of the containers and become unpumpable. When any mixing was employed to the chemical slurry with past methods, it introduced ambient air that weathered off the solvent and created concentrated polymer slurries—again unable to be pumped. These devices have been offered by slurry chemical supply companies out of necessity with nominal functionality. Their design and construction evolved through the need to overcome chemical formulation problem characteristics.
The prior injection apparatus includes screw pumps, gear pumps, positive displacement piston pumps, and direct piston driven diaphragm pumps. All these pumps relied heavily on adequate suction where no plugging occurred. However, the storage and mixing methods and apparatus used prior to this invention did not produce a consistent suction stream, and therefore, failed to pump reliably into the pipeline stream. Even more, the extended periods between injection times caused both suction lines and discharge lines to plug due to settled polymer.
These failures were compounded by poor strainer design and misused metering devices, to name a few. The previously used meters were large oval lobe gear meters designed to pump fluids at 60 gallon per minute. Whereas, the injection rates for most applications were required in the range of 1-5 gallons per hour. These oversized meters were inaccurate. Later on, mass meters were used to achieve more accurate measurement. These meters, at the time, were not designed to handle two phase flow—which is the chemical make up of slurried drag reducing agents.
The prior art had little or no provisions built into the control schemes to warn users of impending failures. They employed simple control loops to take measurements from low precision meters and adjust the pump output via pump stroke adjustments to match the desired set point. No methods or means were used to evaluate the chemical consistency and storage characteristics to warn of eventual failures due to inadequate chemical handing strategies. In addition, these control devices did not meet electrical codes, proved too complicated for the end user, and often could not be integrated into the user's computer logic language because of non-standard and unwieldy operation control language.
It is therefore an object of the present invention to provide an improved and more universal method and apparatus for use in storing, mixing, metering, and pumping polymeric slurries which addresses the deficiencies of the prior art.
3. Objects and Advantages
A principal object of the present invention is to provide a storage and pumping unit for polymeric slurries that will overcome the deficiencies of the prior art devices. Several additional objects and advantages of the present invention are:
(a) to provide a vertical storage vessel having a sloped bottom with a mixing system that will sustain a homogeneous mixture of the slurry over time;
(b) to provide a closed loop vapor recirculation system that will prevent any weathering off effects on the chemical;
(c) to provide a mechanical blower device that will re-circulate vapor and provide the mixing energy for the storage vessel;
(d) to provide a liquid recirculation system that will charge the injection pumps and prevent suction line plugging;
(e) to provide flow switch devices that monitors and alarm recirculation system failures;
(f) to provide a means for measuring storage vessel level that accurately and remotely measures the liquid level in the storage vessel;
(g) to provide a plurality of vapor return distributor jets in the storage vessel that sufficiently agitates and mixes the chemical in the storage vessel;
(h) to provide a means for chemical temperature control device that adjusts the chemical temperature;
(i) to provide a heat barrier that keeps the mechanical components and chemical cool;
(j) to provide an onboard microprocessor to analyze, monitor, and control operation of component parts of the apparatus for storing, mixing, metering and pumping polymeric slurry chemical;
(k) to provide an apparatus for storing, mixing, metering and pumping polymeric slurry chemical that is more universally functional in today's market than the prior art devices by being able to pump any polymeric slurry chemical produced by any manufacturer where the prior art devices are designed to pump only one manufacturer's of polymeric slurry chemical.
It is intended that any other advantages and objects of the present invention that become apparent or obvious from the detailed description or illustrations contained herein are within the scope of the present invention.